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Stable GaX2, InX2 and TlX2 radicals

Abstract

The chemistry of the Group 13 metals is dominated by the +1 and +3 oxidation states, and simple monomeric M(II) species are typically short-lived, highly reactive species. Here we report the first thermally robust monomeric MX2 radicals of gallium, indium and thallium. By making use of sterically demanding boryl substituents, compounds of the type M(II)(boryl)2 (M = Ga, In, Tl) can be synthesized. These decompose above 130 °C and are amenable to structural characterization in the solid state by X-ray crystallography. Electron paramagnetic resonance and computational studies reveal a dominant metal-centred character for all three radicals (>70% spin density at the metal). M(II) species have been invoked as key short-lived intermediates in well-known electron-transfer processes; consistently, the chemical behaviour of these novel isolated species reveals facile one-electron shuttling processes at the metal centre.

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Figure 1: Syntheses of M(II) complexes that feature a supporting bis(boryl) ligand set from either M(I) or M(III) precursors.
Figure 2: Molecular structures.
Figure 3: Field-sweep EPR spectra for 2-Ga, 2-In and 2-Tl measured in frozen pentane/hexane solution (1:1), along with the corresponding simulations.
Figure 4: Redox chemistry of 2-Tl.

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Acknowledgements

We thank the Leverhulme Trust (F/08699/E), the Oxford University John Fell Fund, the Australian Research Council (DP120101300 and FT120100421) and the Engineering and Physical Sciences Research Council (EPSRC) (EP/F019181/1, EP/F055412/1 and access to the NMSF, Swansea). We are grateful for computational resources from the EPSRC's National Service for Computational Chemistry Software, http://www.nsccs.ac.uk), and also thank the University College London's High Performance Computing Facility (Legion@UCL) and associated support services, and the e-Infrastructure South consortium's Centre for Innovation for computing resources via its ‘Iridis’ facility.

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Authors and Affiliations

Authors

Contributions

A.V.P. and D.D. synthesized and characterized the compounds. J.R.H. carried out the EPR studies. C.Y.T., A.D.S., M.J.K., N.P. and C.J. mounted the crystals, collected the single-crystal X-ray crystallographic data and solved the crystal structures. K.H.B. and N.K. carried out the DFT calculations. R.T. carried out the electrochemical measurements. N.K., P.M., C.J. and S.A. generated and managed the project and wrote the manuscript. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Simon Aldridge.

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The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 6896 kb)

Supplementary information

Crystallographic data for compound 2-Ga. (CIF 24 kb)

Supplementary information

Crystallographic data for compound 2-In. (CIF 22 kb)

Supplementary information

Crystallographic data for compound 2-Tl. (CIF 22 kb)

Supplementary information

Crystallographic data for compound 3-Ga. (CIF 38 kb)

Supplementary information

Crystallographic data for compound 3-In. (CIF 37 kb)

Supplementary information

Crystallographic data for compound 4-Ga. (CIF 33 kb)

Supplementary information

Crystallographic data for compound 4-In. (CIF 50 kb)

Supplementary information

Crystallographic data for compound Tl8{B(NDippCH)2}4. (CIF 50 kb)

Supplementary information

Crystallographic data for compound [K(18-crown-6)][2-Tl]. (CIF 45 kb)

Supplementary information

Crystallographic data for compound [2-Tl][B{C6H3(CF3)2-3,5}]. (CIF 116 kb)

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Protchenko, A., Dange, D., Harmer, J. et al. Stable GaX2, InX2 and TlX2 radicals. Nature Chem 6, 315–319 (2014). https://doi.org/10.1038/nchem.1870

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